Life in between the AUs
by DuskmaskGirl3
Summary: Cyndi, a girl half human and monster has lost everything she ever loved after the War. Daughter of a monster and a magician with a SOUL which contains all of the human traits, her magic is very powerful. Many tears came because of her human cousin's abuse. One day she is saved by Ink Sans, who then asks her to help him and the other Sanses stop a certain glitch from destroying AUs.
1. Beginning

Life in between the AUs

 **Hello everyone! My name is Duskmask Girl, it's really nice to finally be here! This is my first time writing fan fiction, so I hope you like this one. Please comment and send feedback so I can make my stories** **better! Without further to say, let's go!**

Cyndi was alone. Broken. Crying. What had she done to deserve this? Was this because she was part monster? Because she had access to ancient power and magic? Because she was different? She didn't know the awnser to any of that. After the humans had sealed the monsters under Mt. Ebott many years ago, she had lost everything. Her happiness, her smile, part of her family. Now she was cursed to live along her human sibling who hated her. Treated her as a freak. Used her as some kind of tool for entertainment.

But it wasn't always like that. Her life used to be perfect in some way. It all started some years before the War: While exploring the woods, a powerful magician who was rumored to have a rainbow SOUL, one with all the human traits combined, met a monster and fell in love with her. They got married and had a girl who also had a rainbow SOUL, and could control various methods of magic. Although not having many human friends, the girl got along with monsters including Asgore Dreemurr and his wife Toriel, who were the Royal Family. She also got along with many of the other monsters; her best friends were a little fish girl with bright red air who loved to fight named Undyne, and the Royal Scientist W.D. Gaster. She was happy. However, her happiness didn't last for long.

One day, war broke between Humans and Monsters. One day, while the battle was tense, they took prisoner her father, accusing him of being a traitor to his own kind. She and her mother hid, but they were found. Before they entered the room they were hiding in, her mother decided to do something to save her daughter. She casted spell on the girl, which would make her age more slowly, handed her a book of spells that belonged to her father, and gave her specific instructions: To stay hidden until the war ended, use her magic to protect herself if needed, and then go look for her father's brother and start living with them as a human. To never reveal her secret to anyone, and to enjoy her life, because it was going to be a long one.

The mother was captured, and sealed underground with the others. She followed the instructions she gave her, and looked for her uncle, who was not in the best mood to welcome someone who caused a loved one to die. They agreed tn take her in, and actually started acting as her second family. But then her cousin came in. He absolutely hated her, and treated her as if she were some sort of old ugly toy. But one day without warning, her uncle and aunt were attacked by a an illness which had no cure. They died some months after that. Now she was alone with her cousin. After he learned about the spell book she had and how she could use magic, her cousin made her use most of her powers to escape life problems and responsibilities.

Her life had become literal hell now. No escape. No hopes of dreams. But despite all of her pain, she stayed strong, Remembering her father's lessons when she needed, staying true to her traits. She stayed DETERMINED.

Little did she know, that freedom would come soon.

One day she was alone reading the spells her mother had left in the book when he came in with his dumb smile.

"Monster! Have you cleaned the kitchen yet?!" He screamed at her "If not, you know what the punishment is right?!"

Cyndi startled

"I-I-I haven't... Yet...I-I'm s-sorry. Please forgive me... I'll do it-"

His smile disappeared. He punched her in the face.

"Stop the polite shit, you freak! You know the rules here right?! When I give you an order, you follow it immediately, got it?! Who was it that accepted you into the family?! My parents right?! The least you can do to honor their death and all they have done for you is to do make my desires come true! You are not supposed to be looking through that garbage book, but being obedient and doing what I say! UNDERSTAND?! MONSTER?!"

She nodded rapidly, but it seemed that wasn't enough. He starting walking towards her with strong fists. Cyndi was hoping that he would forgive her and not hurt her. When he was about to hit her, something stopped his fist. She opened her eyes slowly, and saw a figure standing in front of her. She rubbed her eyes to see if this was a dream, but the figure was still there. The thing returned the punch to her cousin. The impact was so big that it knocked him out of the room. He got up fast and tried to fight back, but the door slammed close. Cyndi was shaking.

"W-who are you...?" She said with a weak voice

The figure turned around and looked at her. After some seconds, she realized the figure was a monster. A skeleton to be exact. He wore a brown scarf, and had strange clothes. In his back he had a giant paint brush with, and had a star in one eye and a little black stain in his cheek. He had smile in his face.

"I'm Ink." He said looking at her "Sorry for the strange enter, but hey, it's better than being punched by some jerk right?"

Ink helped the confused girl stand up

"Anyway, I came her to talk to you" He added "It's something related with your SOUL"

Cyndi got scared. What did another monster want with her soul?

"W-what do you mean..?"

"It's something rather difficult to explain" Ink replied "I need your help for something"

The girl just got even more tangled. He made some black matter appear on his hand and then opened some sort of portal appear. He went in and stared at her.

"Aren't you coming?" He asked

"Who? M-me?" Cyndi replied looking around "W-where?"

"Look, I can't explain right now what's happening. Let's just say that you can either come with me, or stay here and continue being a slave for this guy"

She thought for a moment what to do

"Hey, I can't keep the portal open for so long, are you in or out?"

Cyndi made up her mind. She jumped into the portal and Ink closed it, leaving the girl's room empty and silent.


	2. Magic and favors

Magic and favors

 **Hey guys I'm back! I'm happy to see that you are enjoying the story, so I'll try to update as fast as I can so you don't stay in a cliffhanger forever. Anyways, thanks for reading, and here is Chapter 2!**

The girl opened her eyes expecting to see something, but it was all white. She blinked and rubbed her eyes, but she couldn't see anything, but a blank white void of silence and nothing. Then she remembered everything: the weird skeleton that she had followed, how she had finally escaped, but at the same time confused about everything.

"Hey, I'm here" A voice said while touching her shoulder

She got chills and turned around. It was Ink. Cyndi tried to get away from the surprise, but couldn't feel ground below them. Looking down she realized there was nothing beneath them, and they were floating. Trying to process all this, she got even more scared of what was happening. In an attempt to protect herself from a monster that could be friend or foe, she made a shield with energy from her SOUL. She went into fetal position in fear of what could happen.

"Um, there is no need to waste your energy, I'm not going to hurt you or your SOUL" Ink said tapping gently the bubble

Cyndi raised her head. She still didn't trust him

"What do you want from me...?" She asked "You want my magic? My powers?"

"No, no, no! You've got it all wrong! I won't hurt you! I promise! C'mon, you can break the bubble and see nothing will happen" He replied "Really, I just want you to help me with something really important"

She decided to take the risk and made the shield disappear. She stumbled some moments in the air before getting the hang of being above nothing just floating.

"What is it you want me to do?" She asked firmly "Where are we? What is this place?"

"Oh, yeah, sure, I'll tell you. But first I need to tell you some other things so you understand all of this, got it?" Ink said

Cyndi nodded.

Ink began an explanation as detailed as he could what was happening.

"As you already now, my name is Ink. I am the one in charge of taking care and watching over AUs" He began "What is an AU? Well, to make it simple for you, it's like a variation of our own Universe, being called an Alternate Universe. It's like a tree, it has many branches. They all begin in one Universe, and the choices they do inside it, split it in two, creating an Alternate Universe."

She looked at him a little confused, but trying to understand"Look kid, I'm not the best one making explanations, but you'll get the hang of all this AU thing. So as I was saying, since there are many AUs, there needs to be one who takes care of them, that's me; I check oftenly on them for anomalies on the timelines, or things that could destroy and affect that Universe or another AU. There are many versions of me too, and even of you. The other versions of me are the ones that know about other timelines and AUs, and about me. Other than them, nobody knows about me."

The girl began to understand a bit of what Ink was trying to tell her.

"So, I'm starting to guess what you want me for" She said interrupting his explanation "You were going to ask me to help you to save an Universe or something like that right?"

"I'm glad you mentioned that. Yes, I want you to help me deal with someone who is erasing Alternate Universes. Some time ago, I notices AUs disappearing out of the blue which is very strange to happen like that, so I decided to investigate. One day while looking for the cause, I sensed another one being erased. I rushed to the place and saw a version of me, just standing there. He then turned around with a human soul in his hand, surrounded by blue strings, and shattered it. He then said something that confirmed him being who was destroying all of the Universes. 'I never thought monsters like you would be interested in perserving anomalies like these. I'm really disappointed in you, Ink' He opened a glitching portal and left. Since then, I have tried to track him down, but he never leaves a trail. But one day, he tried to erase the core Universe which made me realize that this became a really serious matter, and that he could destroy everything we ever knew in the blink of an eye without a warning, so much I have taken the decision to stop him immediately or as soon as possible. But I can't do it alone. I'll need all the help needed. Now your magic, is really powerful thanks to your combinatory Human and Monster SOUL, which is why I need you and my other versions to help me on this task."

Cyndi now realized what she had gotten into. She wasn't ready for that kind of responsibility, she couldn't. The girl laughed softly.

"Really, you must be joking right?" Cyndi said "Me? Help you..? No, I can't, I won't be able to, I'm just not strong enough... You say I have a strong SOUL and magic, but I don't really think so"

"I'm not! I'm serious when I say that I need you and others to help me on this task! You **are** strong, I know it! If you just learn how to use it, you will be even more powerful than what you are now! If you want me to, we can train and master your powers. I can **feel it in my bones!** "

The hybrid girl laughed at the joke.

"You really think I can master it? I don't want to mess up and do something to be in the way... I couldn't even... I wasn't even able to save my family... My mother and father are dead and I couldn't even fight... What if I can't?"

Ink grabbed her shoulders and looked at her dead serious

"Kid, look at my eyes when I say this. I know when I sense a strong SOUL, more if their DETERMINATION is very powerful, and I can say yours is. You can do this. You won't be able to save your parents, but you can save the Universes and much more if you believe in yourself and your traits. Don't forget this, and never doubt your magic or choices."

Cyndi saw how much someone actually believed in her. This was new to her. Always being treated as someone inferior, being encouraged to do something by someone was a miracle for her. A miracle she never thought would never happen. Without noticing, she started to cry again. She whipped the tears off.

"Sorry. Thanks for believing in me..." She said with a shaking voice

"Hey kid, that's what friends do right? Don't worry pal, I'm sure you'll do great" Ink replied smiling


	3. Special Training and UnderFell

Special Training

 **Howdy my friends! I'm back again with another chapter baby! Before starting, I wanted to give a shoutout to Transgirl2000 who I think was one if not the first to read this fanfic. Thanks to everyone too for taking time from your day to read through this things I have written, you really help me with all your support when I sometimes don't like the way the story is going and I want to erase it. I know I can't because many people like it and want me to continue it the way it is going at the moment, I really appreciate that! So, without nothing else to say, let's see what Ink Sans has prepared to train Cyndi!**

The girl stood there in front of Ink. Apparently, he was going to teach her how to open portals to other timelines as a first part of her training.

"Ok, kid, pay attention because I need to use a lot of energy to summon a portal." Ink began "The most important thing here in magic is that you concentrate and not freak out. Got it?"

She nodded

"First, you need something to make the portal out of. Usually works best with mirrors and such, but I prefer to use liquids since I can summon ink easily. Next you take the object and focus your magic into it thinking of the place you want to go to. Once you have controlled that, in the case of liquid, tell the object the form you want it to take in your mind and then you cramp all that magic together, shoot it ahead of you and you have a portal! Now try it!"

Cyndi got the instructions, but didn't have a liquid to work with.

"Ink? From what can I make mine?" She asked in a weak voice

"Oh, yeah, you can't create ink right? Here, I'll give you some, but try to just, don't make too much effort, it's easy to hold it"

The skeleton made some of the dark liquid appear on his hand and handed it to the girl. She used some of her magic to hold it floating above her hands. She got surprised at how easy it was to control ink. Cyndi did as the monster had told her, focusing her magic into the little bundle of ink she was holding, but had trouble thinking of where to go. She started to think about other possible versions of her world, and thought of one in which she didn't suffer, one in which her cousin wasn't mean to her, and was a lot stronger with a lot of more confidence and magic. The place she first imagined was a forest, with a monster village near. Then she said in her mind that she wanted an oval shaped portal her size and launched the thing she was holding in front of her. When she opened her eyes again, there was a perfect portal standing before her with the forest she imagined. She looked surprised and happy at the same time knowing she had done it on the first try. Ink also seemed surprised seeing the portal Cyndi had made.

" I-I can't believe I did it..!" She mumbled while panting because she used a lot of energy

"This is the first time I have seen someone do it on their first try! The times I started doing this, my powers would become unstable and so did the portal, but you are maintaining it just fine! But, you could relax a little bit, you know? I can tell you have put a lot of magic and **backbone** into it!"

She laughed again at the pun.

"By the way, where does this lead to..?"

"Ummmm... I don't really know, let me go check in, and I'll tell you later" Ink replied going into the portal "I'll be back soon, so don't try tricks while I'm gone ok?"

"Sure, ok, I don't even t-think I have the energy left... To do that..."

But Ink was already gone. She laid down trying to catch breath. Thinking of how she had done it on her first try, she thought of how she used to doubt her magic and powers, when she also realized the portal was still got a lot of curiosity just imagining the universe she had done a passage to. Remembering Ink's warning, she tried to shake those ideas off her head, but she just couldn't resist going in there.

"Maybe just go and look around and come back... He won't notice if I'm gone for 2 minutes" She thought getting up

She thought about it twice and made up her mind jumping in. Maybe she should have thought about it three times, because the minute she went in, the portal disappeared.

"Oh, damn, now I'm in big trouble"

Cyndi looked around wondering how she could go back when she felt a creepy presence near her. She turned her head looking at her back. Nothing. Looked at her sides. Nothing. She got worried and scared. A shadow came out. Since it was pretty far, she looked at the shape of it. It looked like Ink. She ran towards it shouting Ink's name. When she reached it, she definitely saw how it looked like the monster she knew.

"I'm sorry! I knew I should've stayed where you told me to, but I wanted to explore the place I created a path into! Please, I'm very sorry."

But when she looked throughly at it, she knew it wasn't Ink. He looked like him, but had a black snow-like jacket and a red shirt. His eyes were red and his teeth were spiky. "Please don't tell me he is one of his alternate versions..." Cyndi thought. She knew she had gotten into more trouble than before.

Just then, Ink had returned to the place he lived in.

"Hey, I wanted to tell you that you made a portal to UnderFell! It's one of the most dangerous AUs, so be sure to not go there or-"

But the girl wasn't there

"Oh, no. She went to UnderFell and now she has no way out"


	4. Trapped!

Trapped in UnderFell?

 **Quick announcement, I'll probably upload a chapter almost daily starting from to day because it's my birthday (well it was because I started the chapter yesterday and couldn't finish it on time so I am publishing it now :P) and I wanted to write another one! So here we have the fourth chapter of _Life in between the AUs_!**

She stood frozen in fron of this Universe's version of Ink not knowing what to do. She could only do one thing. _Run_. But her legs didn't want to move. Or they couldn't. Slowly her sight became fuzzy and pitch black, and without knowing it, she passed out. It felt like an eternity the amount of time she slept, and she didn't want it to end. But it had to somehow.

She woke up in a room with red walls. When looking around, all the colors she could see were either black or red. Cyndi tried to get up from the bed she was on, but she couldn't feel her legs. Someone opened the door and stood there. Immediately noticing it was the same monster she saw before passing out, she made the same shield used with Ink to protect herself and went into fetal position again. Tears ran down her face. Although having a lot of power, she had become mentally unstable in the las years, so in delicate, she would usually cry her pain out.

"P-P-please... D-don't hurt me..." She begged crying, shaking as her weak voice came out

He knocked on the magic crystal like shield carefully but violently. Cyndi looked up. The skeleton moved his head side to side, trying to tell her he wouldn't. As she looked at him, she noticed he looked rather nervous. Sweating and blushing made that statement clear for her. Even though minutes and minutes passed, the girl was still scared to break the bubble. Or that was what she planned to do, if she had more energy left inside her. Her magic was running out and she knew it. Thoughts of what could become of her came flooding her mind with even more fear and stress than before. Would her old life come back again? That life of being mistreated and used as a tool? She couldn't think further because of what happened.

The monster punched really hard the shield and the bubble shattered into thousands of tiny pieces of magic that evaporated, one by one into glittering dust. At this moment was when she feared for her life. She looked in every piece of her SOUL for only a little magic to make a weapon for protection, but her body couldn't take it anymore. Closing her eyes and covering the little rainbow heart with her hands, Cyndi hoped for the worst. But nothing happened.

"What the hell are you protecting yourself from? I ain't gonna hurt you" He said

She opened her eyes again and lowered her arms slowly.

"Y-you are n-not going t-to... Hurt m-me...?"

He looked at her confused

"Why should I even waste my time in killing you? Sure, you're human, but nah, not feeling up to it" He replied shrugging "The name's Sans. What's yours kid?"

"Cyndi. Nice to meet you, and first of all, I'm not human. But neither I am a monster like you. I am a hybrid."

Sans had a look that read 'I didn't understand any of that'

"I don't know what do you mean by that, but if you're not human, then we won't have trouble."

"What do you mean?" She asked

"My boss. He is a human hunting FANATIC. If you're not one, then you won't have to deal with that."

The girl was trying to process all of the information when the door opened violently.

"SANS ARE YOU HERE?!" A new voice asked

It looked like it meant trouble for both of them.

"Oh shit it's him" Sans uttered. He turned to Cyndi "Ok kid, just stay quiet and don't get out until I tell you to, he can never enter here. I'll be right back. Don't make a damn noise, got it?!"

She nodded nervously.

"C-coming Boss!" He yelled as he got out.

Now she was alone again, with not a clue of what was happening. Minutes passed when she heard Sans' and the stranger's voices in front of the door.

"I-I swear there is nothing in there!" She heard Sans say

"YOU'RE LYING, I KNOW YOU ARE HIDING SOMETHING" The voice replied "I DEMAND YOU LET ME IN RIGHT NOW"

She got chills running through her spine. She knew she was dead if he came in, and the worst was that she had nothing to defend herself with. In her shock, she decided the only way out was to jump out of the window the room had. Without thinking it twice, she jumped and crystals flew all around the place. Although receiving a lot of fall damage, she used her Determination and started running with all the energy she had left. She ran and ran deeper into de cold forest. She had started to believe she was safe but a sharp pain took over her left leg. Without knowing it, she had stepped on a bear trap which had gotten her leg. Blood dripped from her lower limb and she screamed in pain. It hurted so bad. At this point, she just wanted to die already stop all of her suffering. When she started to lose cociousness, a figure appeared before her. It was Sans again.

"Hey, kid are you alive?!" He screamed shaking her

"J-just... Let me die..." Cyndi replied

Sans somehow opened the trap and got the girl's limb out. He examined it

"Thank god, it didn't crush the bone... Hey, don't pass out! Ugh, shit, what do I do... Don't worry, we'll reach a hospital or someone to treat your leg."

The girl started to feel her whole body go numb. She closed her eyes, and when she opened them again, they were in a kind of laboratory and felt like a needle in her hurt leg. Was she at the doctor? Voices were heard all the time she was unconscious, but listening at the same time. Apparently, someone named Alphys was treating her, and she was going to live. But that didn't matter to her. She just wanted the pain to end. She closed her eyes and when she opened then, the light above her and all the others had gone out. She moved her head towards the left and saw the skeleton asleep on a chair. She moved it towards the right and saw someone, a monster with yellow skin in a lab coat with their head slammed against a computer's keyboard also asleep. She assumed it was night time. And as the others, she went to sleep, again.


	5. The multiverse

The multiverse

 **I'm sorry I'm such a procrastinator! Ugh, I hate it when I forget to upload the next chapter! Sorry guys, my bad, I had a lot of schoolwork during the week, but I'm ready to continue the series starting today! Sorry for the inconvenience :P**

 **\- DuskmaskGirl**

Three weeks had passed and she still couldn't move her leg. Although the injury and skin had been sew together, and had almost healed, she still couldn't make it move. She had stayed at a strange laboratory which belonged to a monster named Alphys the whole time during her recovery. She seemed to be a scientist who had a lot of interest in her magic and rainbow Soul. Everyday, she tried to get up and walk, but it looked like it still wasn't enough recovery she had already gotten. One day she was sitting in the couch trying to read a book when she heard someone come in. Apparently it was a girl judging by the voice.

"DR. ARE YOU HERE?!" The voice screamed

Cyndi leaned her head towards where the sound was coming from and saw the monster who was screaming. It was a fish one apparently, with fish-tail like ears, dark blue skin, a messy ponytail, with one eye patch and black armor with a red broken heart in the middle. Cyndi got a strange feeling of nostalgia when looking at her, but didn't know why. Well, not until what the monster said next.

"IT'S UNDYNE! Ugh, I AM THE CAPTAIN OF THE ROYAL GUARD AND CAN KILL YOU IF DON'T AWNSER ME!"

Then it all made sense. It was her childhood friend, Undyne, the hot-tempered hair she used to play with. She immediately used her magic to lift her body and flew towards her with tears in her face. Undyne noticed someone charging towards her, as if they were attacking, and summoned a spear which appeared on her hand pointing it towards the girl's chest.

"State your identity, punk" She said with a deadly look

"It's m-me! Cyndi! Remember? F-from 11 years ago... We u-used to play a lot..! You always wanted t-to prove your strength fighting everyone you came across... Even me... Don't you remember that...?"

Undyne stared at her for some time. Then, she got those memories on her head too. The spear disappeared and she hugged the girl very tightly.

"Holy shit, are you really that Cyndi from all those years ago?! I can't believe it! I could've sworn I saw you getting killed! How did you get here?!"

"It's kinda of a long story, but I'll tell you later.."

The two friends talked for hours and hours about what had happened in the last years. About how their life had changed after the war, the lost of friends, family.

"Hey, um I have a big question! Undyne, is my mother doing ok? If I'm not wrong she must be here too!"

Undyne looked down, and her smile disappeared. She introduced her hand into her back pocket and took out a necklace. It has a beautiful rainbow colored stone whose shine became a small source of light in the room. It had a metal hawk-like claw which holded the stone. She handed it to the girl.

"Undyne, what is this? Why are you giving this to me?" Cyndi asked looking at it, impressed by its radiance.

She didn't awnser

"H-hey, U-Undyne... Why aren't y-you awnsering m-me...?" She was starting to get worried and her hands began shaking

Again. Silence.

Cyndi started to hope for the worst. Her friend had never left her hanging, and was always smiling and talking, so this kind of behavior became worrying.

"UNDYNE, ASNSER ME, WHERE IS MY MOM?!" She screamed at the top of her lungs.

Undyne stood in silence, and then spoke at last.

"She was killed by a human who fell down here some years ago." Was her response

Cyndi felt like her heart was going to break in two. The only gleam of hope she had left was... Gone...

"She... D-die-"

"YOU HEARD WHAT I SAY, SHE IS DEAD OK?! HER BODY TURNED INTO DUST AFTER BEING SHOT, GET OVER IT!" Undyne screamed with tears on her only eye. "I-I'm sorry that happened. I didn't want it to hit you like this even after your father died, but that is the reality."

The girl didn't listen to the other things Undyne said. She forgot about her injury and ran out of the laboratory. She couldn't accept that her mother was dead. She ran and ran, crying, and with blood dripping from her leg again since the cut had opened once more. She didn't care anymore about this world, she didn't even care is she got more injuries, she just wanted one thing. Death. She opened her eyes a little bit to see where she was going, and saw a waterfall blocking her way. She didn't care and ran right into it, but the she felt something strange. She was floating again in a room similar to Ink's, but it had pages from a notebook (or so it looked) floating everywhere. Cyndi got curious of where she was. She moved towards the nearest page to her and when looking carefully into it, she saw the Undyne she had met running close to the area where the waterfall she had ran into was, probably looking for her. She pushed that page away an looked into another one. This time she saw Undyne in a laboratory that looked exactly like Alphys' with a lab coat and glasses. She was watching cartoons in a big TV. Then a voice speaker to her.

"You are in the multiverse" it said.


	6. Thanks for 200 views! Announcement

Announcement

I just wanted to tell you guys THANKS! For all the views and support we have gotten with the story. Right now we have 200+ views! I'm supper happy tha people like my work and will keep up that way! Right now I'm working on the chapter, and I'm trying to make it the best I can, but I'm having my exams next week, so I may have to delay the publishing of the chapter, I'm sorry again. I also have started using Wattpad! This is my account: DuskmaskGirl.

I don't remember if I did it in Spanish or English, but either way, check it out too! I'm working in another project there! Thanks for the support, and I will see you in the next chapter!

Kyun Kyun Chao~!


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